#define _CRT_SECURE_NO_WARNINGS 1
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
const int N = 2e5 + 10;
vector<char> id[N];

void solve() {
	int n; cin >> n;
	for (int i = 0; i < 26; i++) id[0].push_back(char(i + 'a'));
	for (int i = 1; i <= n; i++) {
		int x; cin >> x;
		char ch = id[x].back();
		id[x + 1].push_back(ch);
		id[x].pop_back();
		cout << ch;
	}
	for (int i = 0; i <= n; i++) id[i].clear();
	cout << endl;
}

int main() {
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	int t; cin >> t;
	while (t--) {
		solve();
	}
	return 0;

}